Battery System

ABSTRACT

A battery system includes a plurality of battery cells and a battery management unit. The battery management unit comprises a plurality of acquisition devices and a plurality of monitoring devices. Each of the acquisition devices is configured to acquire at least one operating parameter of the battery cells associated therewith. Each of the monitoring devices is associated with a plurality of battery cells, and each of the monitoring devices is configured to monitor the operating parameter of the battery cells associated therewith. The battery cells, which are each associated with one of the monitoring devices, are associated with at least two acquisition devices.

The present invention relates to a battery system and to a motor vehiclehaving the battery system according to the invention.

PRIOR ART

It would appear that, in future, new battery systems will increasinglybe used both in stationary applications (for example in wind powerinstallations) and in vehicles (for example in hybrid and electricvehicles), with very stringent requirements being placed on said batterysystems in respect of reliability.

The background to said stringent requirements is that failure of thebattery can result in failure of the entire system. By way of example,in the case of an electric vehicle, failure of the traction batteryleads to a so-called “breakdown”. Furthermore, the failure of thebattery can result in a safety-related problem. In wind powerinstallations, for example, batteries are used in order to protect theinstallation from impermissible operating states in a high wind byvirtue of rotor blade adjustment.

The block diagram for a battery system in accordance with the currentprior art is illustrated in FIG. 1. A battery system, denoted as a wholeby 100, comprises a multiplicity of battery cells 10 and a charging andisolating device 12, which comprises an isolator switch 14, a chargingswitch 16 and a charging resistor 18. In addition, the battery system100 comprises an isolating device 20 having an isolator switch 22.

For safe operation of the battery system 100, it is absolutely necessaryfor each battery cell 10 to be operated within a permitted operatingrange (voltage range, temperature range, current limits). If a batterycell 10 is outside these limits, it must be removed from the cellnetwork. When the battery cells 10 are connected in series (as shown inFIG. 1), failure of a single battery cell 10 therefore results infailure of the whole battery system 100.

In particular in hybrid and electric vehicles, batteries usinglithium-ion or nickel-metal hydride technology which have a large numberof electrochemical battery cells connected in series are used. A batterymanagement unit is used for monitoring the battery and is intended toensure not only safety monitoring but also the longest possible life.For this purpose, the voltage of each individual battery cell ismeasured together with the battery current and the battery temperatureand a state estimation (for example of the state of charge or of thestate of aging of the battery) is made. The evaluated data are passed onto actuators which can act on the cells in a corrective manner (forexample by charge balancing or temperature correction). At the sametime, the battery management unit provides the user with up-to-dateinformation in respect of the state of the battery. In order to maximizethe life, it is helpful always to know the present maximum capacity ofthe battery, that is to say the maximum electrical power which can beoutput or drawn. If this capacity is exceeded, the aging of the batterycan be markedly accelerated.

DISCLOSURE OF THE INVENTION

The invention provides a battery system having a multiplicity of batterycells and a battery management unit. The battery system is preferably alithium-ion battery system.

The battery management unit comprises a multiplicity of acquisitiondevices and a multiplicity of monitoring devices. A multiplicity ofbattery cells is assigned in each case to each of the acquisitiondevices. Each of the acquisition devices is designed to acquire at leastone operating parameter of the battery cells assigned to it. Amultiplicity of battery cells is likewise assigned in each case to eachof the monitoring devices. Each of the monitoring devices is designed tomonitor the operating parameter of the battery cells assigned to it

The battery cells which are assigned in each case to one of themonitoring devices are assigned to at least two acquisition devices.This assignment rule means that the monitoring of the battery cells isoptimized and thus the availability of the battery system is improved.This occurs by virtue of the fact that, in the event of a faultoccurring in one of the acquisition units, although said faultyacquisition unit cannot determine any operating parameters of individualcells anymore, information relating to the absent measurement data canbe obtained through at least one of the monitoring devices assigned inan interlaced manner. In abstracted form, the aim of the invention isthat the monitoring units do not have the same system limits assigned tothem as are assigned to the acquisition units, as a result of which amore precise estimation of the operating parameters by the monitoringunits, and thus a greater reliability and safety of the overall system,can be achieved.

A preferred embodiment of the invention provides that at least one ofthe acquisition devices is designed to acquire the operating parameterfor each individual one of the battery cells assigned to it. Here, thiscan be, in particular, an individual voltage present across eachindividual one of the battery cells. It is further preferred that atleast one of the monitoring devices is designed to determine a sum ofthe values of the operating parameter of all of the battery cellsassigned to said monitoring device. Here, this can be, in particular, atotal voltage present across the entirety of the battery cells assignedto said monitoring device.

A particularly symmetrical distribution or assignment of the batterycells is achieved by virtue of an even number of battery cells beingassigned in each case to at least some of the acquisition devices. In sodoing, in each case half of the battery cells of an acquisition deviceare now assigned to precisely one of the monitoring devices. Inaddition, it is provided in a practical manner that the multiplicity ofbattery cells is grouped into a multiplicity of battery modules. Here,the battery cells of in each case one battery module can be assigned toeach of the acquisition devices.

Cross-system monitoring can be achieved by virtue of those battery cellswhich are assigned to two or more acquisition devices being assigned toat least some of the monitoring devices.

Usually, the same number of battery cells is assigned to at least someof the acquisition devices. This applies in a similar manner in the caseof the monitoring devices.

Finally, the acquisition devices can be components of a fieldbus systemto which the monitoring devices can also optionally be connected.

While it is not necessary for the battery system according to theinvention to have a compact form, a further aspect of the inventionrelates to a battery having a multiplicity of battery cells and abattery management unit which has the above-described technical featuresof the battery system according to the invention as a compact device.

Another aspect of the invention relates to a motor vehicle whichcomprises the battery system according to the invention.

As the whole, the use of the acquisition devices and monitoring devicesachieves a provision of battery systems which can continue to beoperated in a safe manner in the event of failure of one or more batterycells. Admittedly the battery system then has a restricted capacity atthe terminals thereof in certain circumstances as compared to regularoperation, although, with suitable configuration of the battery system,a failure of the system or a safety-critical state of the battery systemcan be avoided.

DRAWINGS

Exemplary embodiments of the invention are explained in more detail withreference to the drawings and the following description. In the figures:

FIG. 1 shows a battery system according to the prior art,

FIG. 2 shows a battery system comprising a multiplicity of acquisitiondevices,

FIG. 3 shows an assignment of acquisition and monitoring devices withrespect to a multiplicity of battery cells according to the prior art,and

FIG. 4 shows an assignment of acquisition and monitoring devices withrespect to a multiplicity of battery cells according to an embodiment ofthe invention.

EMBODIMENTS OF THE INVENTION

FIG. 2 shows a battery system 100 in which a multiplicity of batterycells 10 is connected in series and is grouped into a multiplicity ofmodules 24. A module 24 comprises a predetermined number of, typicallybetween six and twelve, battery cells 10. Acquisition devices 26 measurethe voltage in each case across battery cell 10 and transfer themeasured voltage values to a fieldbus 28 to which an evaluation unit 30is connected. The evaluation unit 30 can actuate a high-voltagecontactor to protect the battery system 100. The fieldbus system 28 inFIG. 2 is interconnected using a bus topology and makes use of a CAN(controlled area network) protocol.

In addition, a multiplicity of monitoring devices 32 (of which only oneis illustrated in FIG. 2) is connected to the fieldbus 28. Themonitoring devices 32 comprise in each case a comparator 34 whichcompares a voltage present across a module 24 with a predeterminedvoltage threshold value V_(s).

If the measured voltage across the module 24 exceeds the voltagethreshold value V_(s), an alarm signal is transmitted to the fieldbus28. In addition, a signal can be transmitted to the fieldbus 28 if apredetermined further voltage threshold value is undershot.

All of the monitoring devices 32 of the battery system 100 can be linkedwith a logic OR gate, which triggers an overall alarm as soon as one ofthe monitoring devices 32 triggers an alarm.

FIG. 3 shows an assignment of acquisition and monitoring devices withrespect to a multiplicity of battery cells, as is known from the priorart. The multiplicity of battery cells 10-1, . . . , 10-12 is groupedinto a multiplicity of battery modules 24-1, 24-2. In contrast to thearrangement illustrated in FIG. 2, the acquisition devices 26-1, 26-2are assigned to the battery cells 10 of in each case one battery module24-1, 24-2. More precisely, by way of example, the acquisition device26-1 is assigned to the six battery cells 10-1, . . . , 10-6 and isdesigned to acquire the individual voltage present across eachindividual one of the battery cells 10-1, . . . , 10-6 assigned to saidacquisition device. The acquisition device 26-1 is thus able to acquiresix individual voltages. Each of the monitoring devices 32-1, 32-2, 32-3is likewise assigned to precisely the battery cells 10 of in each caseone battery module 24-1, 24-2, 24-3 and thus has the same system limitsas the acquisition devices 26-1, 26-2, 26-3. Each of the monitoringdevices 32-1, 32-2, 32-3 is designed to determine the total voltagewhich is present in each case across the battery module 24-1, 24-2, 24-3assigned to said monitoring device. The result of this is that, in theevent of a failure of one of the acquisition devices 26-1 26-2, 26-3,only the total voltage of that battery module in which the technicalfailure occurs can be determined. Information relating to the individualvoltages in said module cannot be obtained, since there is a one-to-oneassignment between acquisition devices 26-1, 26-2, 26-3 and monitoringdevices 32-1, 32-2, 32-3.

For this reason, the invention provides an improved assignment ofacquisition devices and monitoring devices in respect of a multiplicityof battery cells, as illustrated in FIG. 4. The monitoring devices 32,1,. . . , 32-4 are arranged in an interlaced manner with respect to theacquisition devices 26-1, 26-2, 26-3, with the result that they nolonger have the same system limits. More precisely, each of themonitoring devices 32 is assigned in each case to half of a batterymodule and to a further half of an adjacent battery module. By way ofexample, the monitoring device 32-2 is assigned to the battery cells10-4, . . . , 10-9 which in turn are assigned to the battery modules24-1 and 24-2 and the acquisition devices 26-1 and 26-2. In the event ofa failure of the acquisition device 26-2, information relating to theindividual voltages across the individual battery cells 10-7, . . . ,10-12 can be provided by the measured values or other information whichoriginates from the monitoring devices 32-2.

A further monitoring device 36 which is assigned to the battery cells10-1, . . . , 10-12 of two battery modules 24-1, 24-2 is provided. If amultiplicity of monitoring devices 32-1, . . . , 32-4, 36 which provideinformation in each case for different groups of battery cells 10 is nowprovided, then information relating to the individual cells 10 can becollected by means of a control device—not shown.

1. A battery system comprising: a multiplicity of battery cells; and abattery management unit including a multiplicity of acquisition devicesand a multiplicity of monitoring devices, wherein the multiplicity ofbattery cells is assigned in each case to each of the acquisitiondevices, wherein each of the acquisition devices is configured toacquire at least one operating parameter of the battery cells assignedthereto, wherein the multiplicity of battery cells is assigned in eachcase to each of the monitoring devices, wherein each of the monitoringdevices is configured to monitor the at least one operating parameter ofthe battery cells assigned thereto, and wherein the battery cells whichare assigned in each case to one of the monitoring devices are assignedto at least two acquisition devices.
 2. The battery system as claimed inclaim 1, wherein the battery cells are connected in series.
 3. Thebattery system as claimed in claim 1, wherein: at least one of theacquisition devices is configured to acquire the at least one operatingparameter for each individual one of the battery cells assigned thereto,and the at least one operating parameter is an individual voltagepresent across each individual one of the battery cells.
 4. The batterysystem as claimed in claim 1, wherein: at least one of the monitoringdevices is configured to monitor a sum of values of the at least oneoperating parameter of all of the battery cells assigned to the at leastone of the monitoring devices, and the sum of the values of the at leastone operating parameter includes a total voltage present across anentirety of the battery cells assigned to the at least one of themonitoring devices.
 5. The battery system as claimed in claim 1, whereinan even number of the battery cells is assigned in each case to at leastsome of the acquisition devices, of which in each case half are assignedto one of the monitoring devices.
 6. The battery system as claimed inclaim 1, wherein: the multiplicity of battery cells is grouped into amultiplicity of battery modules, and the battery cells of in each caseone battery module are assigned to each of the acquisition devices. 7.The battery system as claimed in claim 1, wherein the battery cellsassigned to at least two acquisition devices are assigned to at leastone of the monitoring devices.
 8. The battery system as claimed in claim1, wherein the same number of battery cells is assigned in each case toat least some of the acquisition devices and/or at least some of themonitoring devices.
 9. The battery system as claimed in claim 1, whereinthe acquisition devices and/or the monitoring devices are components ofa fieldbus system.
 10. A battery comprising: a multiplicity of batterycells; and a battery management unit including a multiplicity ofacquisition devices and a multiplicity of monitoring devices, whereinthe battery forms a battery system, wherein the multiplicity of batterycells is assigned in each case to each of the acquisition deviceswherein each of the acquisition devices is configured to acquire atleast one operating parameter of the battery cells assigned thereto,wherein the multiplicity of battery cells is assigned in each case toeach of the monitoring devices, wherein each of the monitoring devicesis configured to monitor the at least one operating parameter of thebattery cells assigned thereto, and wherein the battery cells which areassigned in each case to one of the monitoring devices are assigned toat least two acquisition devices.
 11. A motor vehicle comprising: adrive system; and a battery system connected to the drive system andincluding a multiplicity of battery cells and a battery management unithaving a multiplicity of acquisition devices and a multiplicity ofmonitoring devices, wherein the multiplicity of battery cells isassigned in each case to each of the acquisition devices, wherein eachof the acquisition devices is configured to acquire at least oneoperating parameter of the battery cells assigned thereto, wherein themultiplicity of battery cells is assigned in each case to each of themonitoring devices wherein each of the monitoring devices is configuredto monitor the at least one operating parameter of the battery cellsassigned thereto, and wherein the battery cells which are assigned ineach case to one of the monitoring devices are assigned to at least twoacquisition devices.